Gruffydd Maelor (died 1191) was Prince of Powys Fadog in Wales.
He is known as Gruffydd Maelor I to distinguish him from his grandson, Gruffydd Maelor II (died 1269).
He was a son of Madog ap Maredudd by Susanna, daughter of Gruffudd ap Cynan. He was to be the founder of the principal ruling family of northern Powys during the 13th century.
On his father's death in 1160 Powys was divided between his three sons (Gruffydd, Owain Brogyntyn and Owain Fychan), a nephew (Owain Cyfeiliog) and a half-brother (Iowerth Goch ap Maredudd).
Gruffydd received Maelor (also known as Bromfield) and Iâl (also known as Yale), as his allotted portion of Powys. He later added Nanheudwy, Cynllaith Owain and Mochnant Is Rhaeadr after the death of his half-brother Owain Fychan in 1187.
His inherited and acquired lands in effect unified and reunited most of northern Powys forming what became known as Powys Fadog after it was inherited by his son.
He married Angharad, his cousin and daughter of Owain Gwynedd, King of Gwynedd.
He died in 1191, leaving issue: